How many sheep graze beneath solar panels can affect both vegetation control and the insects that use the land, according to a three-year Cornell University study at a solar farm in Dryden. A separate Cornell project offers farmers a way to weigh the costs and income of taking on solar-grazing contracts.
At the university-owned Cascadilla Community Solar Farm, researchers compared grazed plots with one maintained by mowing. They found 38% more beneficial insects — including wild bees, honey bees and lady beetles — where two sheep grazed per hectare. Much of that difference came from an 83% increase in honey bees, according to the Cornell report.
The results do not mean adding more sheep will keep increasing insect numbers. At four sheep per hectare, beneficial insect abundance was about the same as in the mowed plot, although the sheep controlled vegetation more effectively than at the lower stocking rate. At eight sheep per hectare, vegetation control was strongest and flock health remained high, but honey bee abundance was 45% lower, Cornell reported.
A trade-off beneath the panels
The field findings appeared Oct. 7 in Environmental Research Letters in a paper led by Leana Zoller, a Cornell postdoctoral associate. She said research often considers sheep grazing and insect habitat separately, even though solar developers and communities must make decisions about both on the same land.
Steve Grodsky, the paper’s senior author and a Cornell assistant professor of natural resources, said stocking rates give farmers a concrete measure they can use. The Dryden results point to a choice: a smaller flock may favor beneficial insects, while a larger one can do more of the vegetation work. The study examined the conditions at one solar farm over three years; its findings should not be treated as a guaranteed result at every site.
Researchers in entomology, ecology, animal and plant sciences took part. Cornell's teaching sheep grazed the plots, and the university's Campus Sustainability Office helped coordinate access with the company managing the solar farm.
Model puts farm finances into the decision
A second Cornell team studied the business side of solar grazing. Its spreadsheet-based model lets farmers estimate how many sheep they need and compare procurement, sales, costs, expected revenue and vegetation at a proposed site. If a flock cannot keep grass below the panels under a contract, the operator may need another way to cut it.
The model, described in a paper published Sept. 28 in Manufacturing & Service Operations Management, grew out of a conversation between Cornell researcher Vincent Slaugh and Caleb Scott, an Ithaca sheep farmer who founded United Agrivoltaics. Cornell researchers Linwei Xin and Shane Henderson also worked on it. United Agrivoltaics has incorporated the tool into its onboarding process, according to Cornell.
Solar developers can use the same calculations to understand what flock sizes and contract terms could work for growers. Cornell said solar contracts can offer farmers both grazing land and a steadier source of income, but the economics depend on a farm’s costs, the available forage and the work required at each site.
Sheep farmer and research co-author Nikola Kochendoerfer, who grazes about 700 ewes at solar installations in New York and Vermont, said some farms she works with are expanding because they are paid to manage vegetation. Whether that opportunity lasts for a particular farm will depend on its contract and operating costs, not simply the presence of a solar array.
FingerLakes1.com is the region’s leading all-digital news publication. The company was founded in 1998 and has been keeping residents informed for more than two decades. Have a lead? Send it to news@fingerlakes1.com.
